BARACUDA-Legend-1

[Janou]

Thanks for theses informations !

[plumabob]

Baracuda kit is here Andy! I gotta say this board is a beauty. Can't wait to get started on it! Before I do, are there any changes I should be aware of?

Thanks,


Bob

[ApBerg]

Baracuda kit is here Andy! I gotta say this board is a beauty. Can't wait to get started on it! Before I do, are there any changes I should be aware of?

Thanks,


Bob

Hello Bob,

Look carfull for the 2n2222 connections E/B/C the symbol on the pcb is NOT leading for how you place the 2N2222, the text for E/B/C is good so look on the data-sheets transistor that you use.
The fets that switch the signal after the NE4434 are importend for good sensetivety, I tested some, not working was the BF245c the b and a versions were O.K.
Think if you can select the 470nF caps on close tolerance( same value) this is good for the sensetivety...

Lots succes and have fun...

Ap

[6666]

Thats a great idea about the sockets

[ApBerg]

Thats a great idea about the sockets

Hello,

Yes, the sockets make testing very easy, no messing up tracks/pads if a other part are inserted.. .But only for bench testing, not for real use ..

As you are from Down Under.... have you seen or have info about the silicon chip logger from December 2010... I made now 2 prototype's , but they are not working good.
I have the 3 magazines and have seen on their website the update's...
Can be that I have made some error in the pcb layout..( pcb is not in the magazines) I like to bay a original pcb board (or kit) but this is not easy...
Think it is a very nice project, that logger, it can log the GPS data and also a lot other inputs e.g. from PI or Magnetometer..

Sorry ... I know it is off topic..

Best regards

Ap

[6666]

Ap i made a new thread in General Electronics

[TH Jim]

Hello ApBerg

Thank you for the info on your experiments using different FET's for gating the signal. Wonder why the best results are when using 2 different FETs? I will get the datasheets and see if i can see any reason. Surely they are both doing almost the same job?

Regards, Jim.

[bernte_one]

thx to forum

[6666]

Hi
so you have found two different fets gives better sensitivity

which fets did you find to be the best combination ?
and how did you connect the Source and Drain for both fets


What was the difference in sensitivity with using a pair of the same fets
compared to using different fets?

thanks
you may have found an important discovery

[plumabob]

Specs for the ultimate baracuda coil anyone? Waiting for some parts to come in. In the meantime I thouight I'd start working on the coil.

Thanks

Bob

[6666]

Good question bob
cct says 24 turns 26 swg 7.5 inch form

Andy would you mind posting a good picture of your completed working Pcb
thanks

6666

[bernte_one]

maybe not the perfect one
but i use a 23cm coil classic single loop (not planar) with 30turns of
H05V-K Litze LIY 0,5 mm (lappkabel or ölflex - product names)
gives 490microH and 1R
the delay trimmer is nearly set to zero
gives a good signal light above 30cm for a 2€ piece

after holidays it will try higher diameter



...ahh 6666 was some seconds faster

[ApBerg]

Hello ApBerg

Thank you for the info on your experiments using different FET's for gating the signal. Wonder why the best results are when using 2 different FETs? I will get the datasheets and see if i can see any reason. Surely they are both doing almost the same job?

Regards, Jim.

Hello Jim

I think it works as follows:

The LF412 (or lm358 ) opamp works as a differents opamp it see's the receive signal from the NE4434 at short time windows .
The timings for that time windows are made with 40106. The fets are the switches that opens that windows so the Lf412 can see the receive signal coming from the NE4434 at time's that have some delay from eats other . The differents in that receive signal makes the 'detect’ signal. It is imported that there is only differents in the signal.. so if components have not the same property's they also give a differents in signal... think that is not what we want...! Think the fets also need a close match ??
Results: select the parts that are in that two 'lines' (ne4434 to lf412) as close as possible..this will give the best sensitivity

If I am wrong of if some have a better explanations...let us know..

Some info http://www.geofex.com/article_folder...h/fetmatch.htm not spot on.. but it give's some info about matching fets..

Best regards

Ap

[TH Jim]

Hello Ap,

Yes I see that it works very similarly to the surfPI (taking a sample of the decay curve and then another after that when the RX signal has died). It is strange why when both FETs are doing essentially the same job - gating a signal from and to the same place that they need to be different???

I'm not getting much depth out of the Barracuda, only about half of what the SurfPI can achieve, and it is particularly poor at finding gold rings. Have my sample delay set at ~ 10uS, this gives best depth, coil is 228mm, 30 turns, 0.5mm enamall, - 435 uH. Also notice my threshold pot needs to be all the way round to one side to get a very faint tone with no target. will have to have another look over and check everything - don't think its running correctly as it is.

Regards Jim.

[ApBerg]

Hello Ap,

Yes I see that it works very similarly to the surfPI (taking a sample of the decay curve and then another after that when the RX signal has died). It is strange why when both FETs are doing essentially the same job - gating a signal from and to the same place that they need to be different???

I'm not getting much depth out of the Barracuda, only about half of what the SurfPI can achieve, and it is particularly poor at finding gold rings. Have my sample delay set at ~ 10uS, this gives best depth, coil is 228mm, 30 turns, 0.5mm enamall, - 435 uH. Also notice my threshold pot needs to be all the way round to one side to get a very faint tone with no target. will have to have another look over and check everything - don't think its running correctly as it is.

Regards Jim.

Hello Jim,

Look also at the offset adjustment from the Ne4434, with some coils setting the offset at zero volt I also had low sens. It is the combination from the offset and the time delay that make the good sens.... The extra fet with the switch option... is the key to succes ???? If somebody can explain ??

Best regards.

Ap